Microsoft announced the end of life of Silverlight 5 in 2012. In 2013, Microsoft announced that they had ceased development of Silverlight except for patches and bugfixes. Microsoft has set the support end date for Silverlight 5 to be October 2021.[6] Silverlight is no longer supported in Google Chrome since September 2015.[7] Since Microsoft Edge does not support plugins, it also does not support Silverlight.[8]

Silverlight was used to provide video streaming for the NBC coverage of the 2008 Summer Olympics in Beijing,[9] the 2010 Winter Olympics in Vancouver,[10] and the 2008 conventions for both major United States political parties.[11] Silverlight was also used by Amazon Video and Netflix for their instant video streaming services,[12][13] but Netflix said in its Tech Blog in 2013 that, since Microsoft had announced the end of life, they would be moving to HTML5 video.[14]

A free software implementation (now abandoned)[21] named Moonlight, developed by Novell in cooperation with Microsoft, was released to bring Silverlight versions 1 and 2 functionality to Linux, FreeBSD, and other open source platforms, although some Linux distributions did not include it, citing redistribution and patent concerns.[22] However, in May 2012, Moonlight was abandoned because of its lack of popularity.[23]

According to statowl.com, Microsoft Silverlight had a penetration of 64.16% on May 2011. Usage on July 2010 was 53.54%, whereas as of May 2011[update] market leader Adobe Flash was installed on 95.26% of browsers, and Java was supported on 76.51% of browsers.[24] Support of these plugins is not mutually exclusive; one system can support all three. Not all Web sites require a browser plugin; of those that do, as of 26 August 2011[update], fewer than 0.3% sites used Silverlight and Java,[25] 27% used Adobe Flash,[26] although another source cites around 4% for Java.[27]

Many users complain that Microsoft presents Silverlight repeatedly as a Windows Update even if the user has not installed Silverlight. Microsoft ships a non-functional version of Silverlight with some versions of Windows and prompts the user to install Silverlight for each version of Silverlight released.[28] Microsoft continues to prompt users to install Silverlight despite informing developers to stop supporting it, and having forgone support for Silverlight in its own Microsoft Edge browser.[29]

Over the course of about five years Microsoft released five versions with varying platform support: The first version was released in 2007; and the fifth (and final) major version on May 8, 2012. It is compatible with later versions of Internet Explorer and Mozilla Firefox web browsers on Microsoft Windows (except Windows RT) operating systems,[30] with Firefox and Safari under Mac and OS X, and with mobile devices using the Windows Mobile[31] and Symbian (Series 60)[32] platforms.

Cross platform Mozilla Firefox support for Silverlight is expected to be removed as of the end of 2016 when Mozilla removes support for NPAPI plugins,[33] bringing it in-line with the removal of NPAPI plugin support in Google Chrome.[34][35]

Upcoming Opera support was promised since May 3, 2007, when David Storey, the Chief Web Opener at Opera, revealed a Microsoft poster for MIX conference that had shown Opera integration as a part of Silverlight 1.1.[39] However, Opera was never officially supported by Silverlight.

On Linux and FreeBSD, the functionality is available via Moonlight.[40][41] Moonlight is available for the major Linux distributions, with support for Firefox, Konqueror, and Opera browsers, provided it was obtained through Novell.[42]Miguel de Icaza has expressed an interest in working with developers from other operating systems (BSD, Solaris) and other browsers (Konqueror, WebKit and Opera) to ensure that Moonlight works fine on their systems.[43] Availability of Moonlight version 1.0 for FreeBSD was announced in March 2009,[44] but has since been reported not to actually work.[45] As of 2011[update], the current version of Moonlight (4 Preview 1) does not officially work on new versions of Firefox (newer than 3.x) on GNU/Linux-based operating systems. However, it can be installed in an unofficial way (for example using the Add-on Compatibility Reporter add-on) and with Firefox 11 it works correctly when installed. As noted above, the Moonlight project was abandoned in May 2012.
As of 2013[update], Pipelight is available. It is a plugin for Linux browsers which, when combined with Wine, enables Windows browser plugins, including Silverlight, to run.[46]

Silverlight was the primary development environment for Windows Phone and is based on Silverlight 4. For previous versions of Windows Mobile, the first Community Technology Preview (CTP) for Windows Mobile 6 was expected in the second quarter of 2008, but it still has not been officially announced. Microsoft has stopped focusing on bringing Silverlight to Windows Mobile 6.x.[47]Nokia announced plans to make Silverlight for Mobile available for S60 on Symbian OS, as well as for Series 40 devices and Nokia internet tablets[48][49] (while it later sold the business to Microsoft and now sells Android tablets and will sell Alcatel-Lucent branded smartphones). Silverlight for Mobile supports Silverlight 2 content and .NET languages.[31] Silverlight for Windows Phone 7.5 is based on Silverlight 4.[50]

Silverlight applications can be written in any .NET programming language. As such, any development tools which can be used with .NET languages can work with Silverlight, provided they can target the Silverlight CoreCLR for hosting the application, instead of the .NET Framework CLR. Microsoft has positioned Microsoft Expression Blend as a companion tool to Visual Studio for the design of Silverlight User Interface applications. Visual Studio can be used to develop and debug Silverlight applications. To create Silverlight projects and let the compiler target CoreCLR, Visual Studio requires the Silverlight Tools for Visual Studio.[51]

A Silverlight control is a ZIP format file with extension .XAP containing a list of one or more .NET managed assemblies (.DLL files) along with the AppManifest.XAML file containing this list along with the entry point (class and assembly). It can be hosted in any HTML file using an object tag, for example:

A Silverlight project contains the Silverlight.js and CreateSilverlight.js files which initializes the Silverlight plug-in for use in HTML pages, a XAML file for the UI, and code-behind files for the application code. Silverlight applications are debugged in a manner similar to ASP.NET applications. Visual Studio's CLR Remote Cross Platform Debugging feature can be used to debug Silverlight applications running on a different platform as well.[52]

In conjunction with the release of Silverlight 2, Eclipse was added as a development tool option.[53]

An April 2007 to 2008 PC World report suggested that Microsoft intended to release certain parts of Silverlight source code as open source software,[54] but a week later Sam Ramji, director of platform technology strategy at Microsoft, contradicted the rumors by confirming that the company had no plans to open Silverlight.[55] Some controls that ship with Silverlight are available under the Microsoft Public License as a part of a separate project known as the Silverlight Toolkit.[56]

Silverlight's proprietary nature is a concern to competition since it may harm the open nature of the World Wide Web. Advocates of free software are also concerned Silverlight could be another example of Microsoft's embrace, extend and extinguish strategy.[57] Both Microsoft Silverlight and Adobe Flash are proprietary.[58] Flash's file formats are publicly documented standards,[59][60] as are Silverlight's.[61][62] However, the communication between a Flash player and a server is done by the proprietary protocol RTMP. Both Flash and Silverlight use patent-encumbered audio and video codecs.

The project had been officially supported by Microsoft which,[40] under an agreement with Novell, made not-publicly-available additional specifications, access to the Silverlight Base Class Library APIs, binary codecs and test cases available to the Mono team.[41][65]

The "covenant" under which Novell was granted this exclusive access also specified conditions incompatible with the licensing that covers most free and open source software. As examples, it specifically required that the software must have been "obtained directly from Novell or through an Intermediate Recipient" and that it must be "not licensed under GPLv3 or a Similar License".[42] Some free software proponents criticized the covenant.[66]

Silverlight was criticised for not living up to its cross-platform operating system compatibility promises, especially on Linux systems, compared to its extensive support on Apple and Microsoft desktops for Internet Explorer, Firefox, and Chrome. Although Microsoft was officially collaborating on the Moonlight project, Bruce Chizen, CEO of Adobe Systems, which sells the competing proprietary Flash platform, questioned "the commitment of Microsoft to keep the Silverlight platform compatible with other OS besides Windows".[67] His concerns are based on "examples from history" where he said that Microsoft had launched products with promises of ongoing cross-platform compatibility that no longer apply, for example Internet Explorer for UNIX and Windows Media Player for Mac.

In 2007, California and several other U.S. states asked a district judge to extend most of Microsoft's antitrust case settlement for another five years,[68] citing "a number of concerns, including the fear that Microsoft could use the next version of Windows to 'tilt the playing field' toward Silverlight, its new Adobe Flash competitor," says a Seattle Post-Intelligencer article. The final judgment on the motion extended the settlement two years, to November 2009, but for reasons unrelated to Silverlight.[69] In Windows 7 the Silverlight web browser plug-in is not installed automatically, but is a downloadable optional update through Windows Update.[70]

Silverlight 1 – Silverlight 1, developed under the codename Windows Presentation Foundation/Everywhere (WPF/E) was released in 2007. It consisted of the core presentation framework, which is responsible for the user interface (UI), interactivity and user input, basic UI controls, graphics and animation, media playback, Digital rights management (DRM), and DOM integration.

Silverlight 2 – Included a version of the .NET Framework, implemented the same full Common Language Runtime (CLR) version as .NET Framework 3.0; so it can execute programs written in any .NET language.

Silverlight 3 – Silverlight 3 was announced on September 12, 2008, and unveiled at MIX09 in Las Vegas on March 18, 2009.[71] A beta version was made available for download the same day. The final version was released July 9, 2009. Silverlight 3 included more controls[72]—including DataGrid, TreeView, various layout panels, DataForm for forms-driven applications and DataPager for viewing paginated data.

Silverlight 4 – On November 18, 2009, at the Professional Developers Conference in Los Angeles, Microsoft Corporation unveiled a Beta version of Silverlight 4.[73] The final version was released on April 15, 2010 (along with Silverlight 4 tools for developers). New features in Silverlight 4 include: Support for Google's Chrome browser, webcam and microphone, printing, more mouse support, new notification support to send messages to users, new and enhanced controls (e.g., RichTextBox, DataGrid), theming of controls, rendering HTML, better localization, etc....

Silverlight 5 – The official release was made available to download officially on December 9, 2011.[74] New features include GPU accelerated video decoding, 3D graphics, playback speed controls, remote control, and 64-bit support.[74]

^ ab"Covenant to Downstream Recipients of Moonlight – Microsoft & Novell Interoperability Collaboration". Microsoft. September 28, 2007. Retrieved March 8, 2008. “Downstream Recipient” means an entity or individual that uses for its intended purpose a Moonlight Implementation obtained directly from Novell or through an Intermediate Recipient… Microsoft reserves the right to update (including discontinue) the foregoing covenant… “Moonlight Implementation” means only those specific portions of Moonlight 1.0 or Moonlight 1.1 that run only as a plug-in to a browser on a Personal Computer and are not licensed under GPLv3 or a Similar License.

^"Microsoft/Novell Collaboration on Silverlight". Miguel de Icaza. September 5, 2007. Retrieved November 9, 2008. We will be supporting Firefox and Linux initially (that is our first goal) but we are looking forward to work with developers from other operating systems (BSD, Solaris) and other browsers (Konqueror, WebKit and Opera) to ensure that Moonlight works fine on their systems.

^"What's New in Silverlight for Windows Phone". MSDN. Microsoft Corporation. Retrieved August 26, 2011. Silverlight for Windows Phone OS 7.1 is based on Silverlight 4. That means if you create a new Silverlight for Windows Phone application that targets Windows Phone OS 7.1, you can take advantage of several new features.

^Markoff, John (August 11, 2008). "Microsoft leveraging Silverlight and riling critics". International Herald Tribune. Retrieved January 11, 2009. Others take a darker view of Microsoft's intentions and argue that Silverlight is simply a rehash of the company's 1990s-era "embrace and extend" strategy for pre-empting Web competition. "They're still playing the same games," said Michael Nelson, professor of internet studies at Georgetown University. "It's a way to lock up the content, and it's not enabling as much innovation as we would like to see."

^Meyer, David (April 30, 2008). "Mozilla warns of Flash and Silverlight 'agenda'". ZDNet. Retrieved January 11, 2009. Companies building websites should beware of proprietary rich-media technologies like Adobe's Flash and Microsoft's Silverlight, the founder of Mozilla Europe has warned.

^Jones, Pamela (May 28, 2008). "Shining Some Light on Microsoft's Moonlight Covenant". Groklaw. Retrieved August 25, 2008. Moonlight is safe from threat only if you get it from Novell AND DO NOT PASS IT ON, as there are no protections for downstream recipients...Unless those downstream recipients get it from an 'Intermediate Recipient' defined to only include authorized resellers...It's like walking into a store and saying "I'm only going to pay half of the amount I owe and I hereby disclaim my duty to pay full price." You can try that, but the law supersedes whatever intent or desire you've expressed. At minimum, this shows how clearly they DO NOT want to coexist with GPL'd code.